The molecular and behavioral aspects of α-pyrrolidinopentiophenone (α-PVP) have been characterized; however, how the structural modification of α-PVP affects its abuse potential is still unknown. In this study, we investigated the abuse potential of two pyrrolidinylated second-generation cathinones:4-chloro-α-pyrrolidinopentiophenone (4cl-α-PVP) and 4-chloro-α-pyrrolidinopropiophenone (4cl-α-PPP). Male Sprague-Dawley rats were trained to self-administer methamphetamine (METH, 0.05 mg·kg-1·infusion-1), α-PVP (0.05 mg·kg-1·infusion-1), 4cl-α-PVP (0.05 mg·kg-1·infusion-1), and 4cl-α-PPP (0.5 mg·kg-1·infusion-1) under a fixed ratio (FR) 1 reinforcement schedule for 10 sessions. The discriminative-stimulus effect of METH (0.8 mg/kg) from saline was tested under an FR10 schedule of food delivery. α-PVP, 4cl-α-PVP and 4cl-α-PPP produced reinforcement behaviors and presented an inverted U-shaped dose effect. The reinforcing potency was displayed with a rank order of α-PVP (0.029 mg·kg-1·infusion-1) > METH (0.040 mg·kg-1·infusion-1) > 4cl-α-PVP (0.094 mg·kg-1·infusion-1) > 4cl-α-PPP (0.51 mg·kg-1·infusion-1). All three drugs were fully substituted for the discriminative-stimulus effects of METH in rats. The substitution potency for discriminative-stimulus effects of α-PVP (ED50 = 0.4 mg/kg) was approximately equal to that of METH (ED50 = 0.3 mg/kg), while the discriminative potency of 4cl-α-PVP (ED50 = 1.0 mg/kg) and 4cl-α-PPP (ED50 = 5 mg/kg) was approximately 3 and 16-fold less than that of METH. The rank order of potency was α-PVP ≈ METH >4cl-α-PVP > 4cl-α-PPP. The present data demonstrated that 4cl-α-PVP and 4cl-α-PPP produced reinforcing effects and fully and dose-dependently substituted for the subjective effects of METH, suggesting that both 4cl-α-PVP and 4cl-α-PPP have abuse potential that may be similar to METH.
Keywords: Abuse liability; Cathinone; Methamphetamine; New psychoactive substance; Reinforcement.
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